APPLICATION OF GIS TO THE EFFECTIVE MANAGEMENT OF GULLY EROSION IN ANAMBRA STATE

INTRODUCTION What is Gully Erosion? It is the removal of soil along drainage lines by surface water run-off. How do they Occur? They occur when water is channeled across unprotected land and washes away the soil along drainage lines.

Gully Site in Obosi in Onitsha South L.G.A, Anambra State

Causes of Gully Erosion The main cause are: Deforestation Excavation Soil Saturation Poor Drainage Other causes include Groundwater Sapping and Anthropogenic causes

Gully Erosion in Anambra There are over 100 gully sites in Anambra distributed in various local governments

Objectives of the Project To create a digitized map of Anambra State showing all gully erosion sites. To create a database of all necessary data needed in the control of gully erosion. To use the graphical and textual data to create a functional G.I.S To proffer solutions to the problems of gully erosion in Anambra State

Methodology Applied Acquisition of Data Classification of Data Database Design Conversion of Data Storage of Data

Result and Analysis Digital Maps of Anambra State in G.I.S format: Map showing gully erosion sites in L.G.A Map showing population density in L.G.A Map showing soil texture of the state Topo Map of Anambra

Analysis The results shows that topography, soil texture, and population density contributed a lot to erosion in Anambra. There are more gullies in the areas of higher gradient (i.e. Aguata) than in the areas of lower plane ( i.e. Onitsha). Also shows that gullies are more in the areas that has loamy soil and this areas has the sharpest gradient. Onitsha is sandy and mostly populated but has the lowest number of gullies because its almost on a level plane.

Map showing population density of Anambra

Map showing soil texture

Topographic Map of Anambra

Map showing flood patterns

Query showing proximity of gully sites to roads N.B The state map theme was unchecked

Charts Fig 15a: Graph Showing the Percentage of Controlled to Uncontrolled Gully Sites in Anambra State.

Graph Showing Number of Gully Sites in each L.G.A of Anambra State.

Conclusion The success of any gully control measure undoubtedly depends on the stage of gully development, the local geological setting (stratigraphy and groundwater conditions), the characteristics and hydro-geotechnical properties of the eroded soils and their response to varying meteorological and hydrological conditions G.I.S and its related technology will help greatly in the acquisition, organization, management and analysis of these large volumes of data, allowing for better understanding of natural disasters and the importance of record for future use.

Recommendations This method of monitoring and controlling the gully erosion can also be applied throughout the Nation. Data acquisition is rather stressful; hence the Federal Government should support research financially in order to ease acquisition procedures. The Federal Office of Statistics should increase the scope of data which they acquire so that one may easily acquire data from them. Students who engage in expensive projects such as this should be supported in all ramifications especially due to the costly nature of such projects.